Vacuum energy in a spherically symmetric background field

The vacuum energy of a scalar field in a spherically symmetric background field is considered. It is expressed through the Jost function of the corresponding scattering problem. The renormalization is discussed in detail and performed using the uniform asymptotic expansion of the Jost function. The method is demonstrated in a simple explicit example.Comment: 14 pages, 1 Postscript figur

Consumer Preferences for Cluster Raisins: A Focus Group Investigation

The U.S. raisin industry has experienced a decline in acreage and in number of growers in recent years. One firm is trying a novel approach to marketing raisins, namely, by marketing them still attached to the vine. This product is called cluster raisins. In order to explore consumer preferences related to cluster raisins, and to generate new product ideas and preferred marketing methods, two focus group interviews were implemented. Findings included that a young (i.e., 18 - 25 years) market segment would be a recommended target market. Also included are recommendations regarding price, packaging, and methods of increasing consumer awareness. Recommended marketing channels include specialty markets (e.g., Trader Joe's or Whole Foods) and gift baskets.Marketing,

Implications of LEP Results for SO(10) Grandunification with Two Intermediate Stages

We consider the breaking of the grand unification group $SO(10)$ to the standard model gauge group through several chains containing two intermediate stages. Using the values of the gauge coupling constants at scale $M_Z$ derived from recent LEP data, we determine the range of their intermediate and unification scales. In particular, we identify those chains that permit new gauge structure at relatively low energy $(\sim 1\, {\rm TeV})$.Comment: (LATEX, 9 pages + 3 pages of figures not included) OITS-48

The effect of polar lipids on tear film dynamics

In this paper we present a mathematical model describing the effect of polar lipids on the evolution of a precorneal tear film, with the aim of explaining the interesting experimentally observed phenomenon that the tear film continues to move upwards even after the upper eyelid has become stationary. The polar lipid is an insoluble surface species that locally alters the surface tension of the tear film. In the lubrication limit, the model reduces to two coupled nonlinear partial differential equations for the film thickness and the concentration of lipid. We solve the system numerically and observe that the presence of the lipid causes an increase in flow of liquid up the eye. We further exploit the size of the parameters in the problem to explain the initial evolution of the system

Collision-Induced Decay of Metastable Baby Skyrmions

Many extensions of the standard model predict heavy metastable particles which may be modeled as solitons (skyrmions of the Higgs field), relating their particle number to a winding number. Previous work has shown that the electroweak interactions admit processes in which these solitons decay, violating standard model baryon number. We motivate the hypothesis that baryon-number-violating decay is a generic outcome of collisions between these heavy particles. We do so by exploring a 2+1 dimensional theory which also possesses metastable skyrmions. We use relaxation techniques to determine the size, shape and energy of static solitons in their ground state. These solitons could decay by quantum mechanical tunneling. Classically, they are metastable: only a finite excitation energy is required to induce their decay. We attempt to induce soliton decay in a classical simulation by colliding pairs of solitons. We analyze the collision of solitons with varying inherent stabilities and varying incident velocities and orientations. Our results suggest that winding-number violating decay is a generic outcome of collisions. All that is required is sufficient (not necessarily very large) incident velocity; no fine-tuning of initial conditions is required.Comment: 24 pages, 7 figures, latex. Very small changes onl

Retrospective model-based inference guides model-free credit assignment

An extensive reinforcement learning literature shows that organisms assign credit efficiently, even under conditions of state uncertainty. However, little is known about credit-assignment when state uncertainty is subsequently resolved. Here, we address this problem within the framework of an interaction between model-free (MF) and model-based (MB) control systems. We present and support experimentally a theory of MB retrospective-inference. Within this framework, a MB system resolves uncertainty that prevailed when actions were taken thus guiding an MF credit-assignment. Using a task in which there was initial uncertainty about the lotteries that were chosen, we found that when participants’ momentary uncertainty about which lottery had generated an outcome was resolved by provision of subsequent information, participants preferentially assigned credit within a MF system to the lottery they retrospectively inferred was responsible for this outcome. These findings extend our knowledge about the range of MB functions and the scope of system interactions

The Stability of the Weak Skyrmions

We consider a set of gauge invariant terms in higher order effective Lagrangians of the strongly interacting scalar of the electroweak theory. The terms are introduced in the framework of the hidden gauge symmetry formalism. The usual gauge term is known to stabilize the skyrmion but only in the large vector mass limit. We find that adding higher-order gauge terms is insufficient to insure stability. We then proceed to analyze other gauge invariant interaction terms. Some of the conclusions also apply to QCD skyrmions.Comment: 3 pages, revtex v3, (optional), LAVAL-PHY-11-9

A New Phase Speciation Leaching Procedure for the Determination of Metals in Oxic and Anoxic Sediments

Toxic trace elements such as cadmium, lead, chromium, and arsenic released by human activities can accumulate in marine and estuarine sediments, where these metals are often sequestered until local environmental changes (e.g., redox, salinity, and/or pH) allow these elements to be reintroduced into the food web. In order to assess the extent of toxic trace element contamination in sediment, numerous leaching schemes have been developed that separate sediment-bound trace metals into operationally defined geochemical phases. These phase speciation leaching schemes are typically designed with the purpose of being used on either oxic or anoxic sediments. However, natural sediments often contain prominent redox boundaries; therefore, it is useful to develop a single phase speciation leaching scheme which can be used on both oxic and anoxic sediments. A six step leaching scheme was developed in order to separate sediment-bound trace elements into five operationally defined phases: exchangeable, oxide, acid volatile sulfide (AVS), organic, and pyrite. The efficacy of five of the six leaching steps (oxide, AVS, organic #1 and #2, and pyrite) was evaluated using standard reference sediments (NIST 2702 and BCR-701) and actual sediment samples. Overall, the results show that the six step leaching process compared well with other frequently utilized phase speciation leaching schemes ( Tessier and optimized BCR ). With the exception of some surface sediment oxides carrying over into the AVS phase, the leach AVS and pyrite results compared well with H2S generation sediment sulfide analysis methods. The organic phase extractions were about three times more effective (∼60% removal efficiency) at removing labile organic material (e.g., proteins and humic and fulvic acids) in sediment than refractory organics (e.g., protokerogens) (∼20% removal efficiency). The six step leach method was applied to bulk sediments obtained from three estuaries with differing geochemical environments (salinity and sediment C and S concentrations). The sediment phase speciation results for the major (Fe, Mn, and Ca) and trace metals (Cd, Pb, Cr, and As) of interest are similar to those reported by other workers for similar environments, with the majority of the trace metals being located in the oxide and organic phases

A mediation approach to understanding socio-economic inequalities in maternal health-seeking behaviours in Egypt.

BACKGROUND: The levels and origins of socio-economic inequalities in health-seeking behaviours in Egypt are poorly understood. This paper assesses the levels of health-seeking behaviours related to maternal care (antenatal care [ANC] and facility delivery) and their accumulation during pregnancy and childbirth. Secondly, it explores the mechanisms underlying the association between socio-economic position (SEP) and maternal health-seeking behaviours. Thirdly, it examines the effectiveness of targeting of free public ANC and delivery care. METHODS: Data from the 2008 Demographic and Health Survey were used to capture two latent constructs of SEP: individual socio-cultural capital and household-level economic capital. These variables were entered into an adjusted mediation model, predicting twelve dimensions of maternal health-seeking; including any ANC, private ANC, first ANC visit in first trimester, regular ANC (four or more visits during pregnancy), facility delivery, and private delivery. ANC and delivery care costs were examined separately by provider type (public or private). RESULTS: While 74.2% of women with a birth in the 5-year recall period obtained any ANC and 72.4% delivered in a facility, only 48.8% obtained the complete maternal care package (timely and regular facility-based ANC as well as facility delivery) for their most recent live birth. Both socio-cultural capital and economic capital were independently positively associated with receiving any ANC and delivering in a facility. The strongest direct effect of socio-cultural capital was seen in models predicting private provider use of both ANC and delivery. Despite substantial proportions of women using public providers reporting receipt of free care (ANC: 38%, delivery: 24%), this free-of-charge public care was not effectively targeted to women with lowest economic resources. CONCLUSIONS: Socio-cultural capital is the primary mechanism leading to inequalities in maternal health-seeking in Egypt. Future studies should therefore examine the objective and perceived quality of care from different types of providers. Improvements in the targeting of free public care could help reduce the existing SEP-based inequalities in maternal care coverage in the short term